Display screen or portion thereof with a graphical user interface



The FIGURE is a front view of a display screen or portion thereof with agraphical user interface showing the claimed design.

The broken lines are included for the purpose of illustrating portionsof the display screen or portion thereof with a graphical user interfacethat form no part of the claimed design.

CLAIM The ornamental design for a display screen or portion thereof witha graphical user interface, as shown and described.